As soon as a chemical is spilled it becomes a pollutant, but the fate of that pollutant depends to a large degree on its chemistry, which determines how it will partition to various “compartments,” or phases, of the environment. This idea is enshrined in risk‐based strategies for assessing contaminated land and water. In many cases a contaminant spill on land quickly becomes a water pollution issue, be it surface or groundwater. As many countries are heavily reliant on groundwater as a source of potable water, investigating the fate of pollutants is an essential prerequisite to any remedial action plan for contaminant cleanup.

Partitioning is governed by some fundamental properties of chemicals, but partitioning should be viewed in relation to the toxicity of the chemical in question and its degradability in the various environmental compartments. In this article, the important properties of chemicals that relate to partitioning are examined, and the theory is reinforced by example. The examples chosen are benzene, phenol, and some chlorinated phenols. All of these compounds are important industrial chemicals.

Bioavailability is a simple concept, but practically it is a complex issue that remains to be resolved. The bioavailability concept is also enshrined in the risk assessment approach to contaminated land and water. If a pollutant is present in soil or water in high concentration, but is not available to the biota, then surely it presents minimal risk. Regardless of the apparent simplicity of the concept, there is great urgency to find methods for quantifying bioavailability. Some approaches to solving this quandary are discussed.